Various types of apparatus have been introduced into the marketplace to provide collision avoidance operation of motor vehicles, principally for collision avoidance of automobiles and light trucks. Most of these systems have been specifically designed for automobiles and light trucks which use hydraulic brake systems. In a hydraulic brake system, brake fluid is used to transmit a hydraulic pressure from the driver's pedal to the foundation brakes, with or without vacuum assistance to increase the pressure. Braking force is dependent to a large measure upon the pressure developed by pressing the brake pedal.
Included in such collision avoidance apparatus are object detection and ranging systems using radar, laser, or optical camera ranging technology to trigger an alarm to the driver, or to adjust the setting of automatic cruise control, or to activate an automated braking system structure.
These systems serve to reduce or eliminate the effect of human reaction time in the presence of a collision threat. They are generally intended for OEM, factory installation.
Present day collision alarm and avoidance systems usually take the form of a warning system or a supplemental brake control system which is microprocessor driven. Some of these systems prematurely control brake light illumination of a proceeding vehicle, as a distance closure warning to a following vehicle, before the brake pedal of the preceding vehicle is operated. Other systems calculate collision mitigation based upon radar, yaw rate, wheel speed, and rear view camera inputs to control power brake booster performance to adjust braking force in a hydraulic system. Many of these systems have electronic controllers which calculate velocity profiles, collision probabilities and provide supplemental brake system instructions.
Braking systems for heavy commercial highway vehicles, such as tractor trailers, heavy straight trucks, and buses, depart from the hydraulic automobile and light truck braking systems, as they are almost exclusively air brake systems. Air brakes can develop a greater stopping force, use simpler components, remain operable even in the presence of a leak, and are generally more safe than hydraulic brakes. Air brakes are found on commercial vehicles with a maximum gross vehicle weight rating (GVWR) of 33,000 pounds or more. They are also often found on vehicles with lesser GVWR, such as 20,000 pounds.
Commercial vehicle air brake systems operate with air pressure from air reservoirs containing a volume of high pressure air, ranging from 60 psi to 120 psi (maximum allowed by D.O.T.), depending upon the design of the braking system. Typically, air reservoirs used in air brake systems are under a pressure of 60-120 psi. There generally is a front circuit to operate the front brakes and a rear circuit to operate the rear brakes. Each circuit has its own air reservoir.
Fail safe air brake systems provide a lesser pressure to service (work) brakes from a second air reservoir in the presence of a failure in the primary service brake circuit. Other systems utilize a lower pressure circuit to control the relay valves of a higher pressure service brake circuit.
Factory available adaptive cruise control systems can electronically set a braking pressure in an air brake system above the default braking pressure, as software resident in the system senses and calculates vehicle factors including speed, yaw rate, lateral acceleration steering angle and traction in regards to predetermined limits for any of these vehicle factors. If the limits are not exceeded, a pressure above the default braking pressure is applied. This process is successively conducted and the pressure is successively increased, based on the successive monitoring and calculating of values in comparison to the predetermined factor limits, until a vehicle deceleration rate of about 2 meters per second is achieved, if possible. Further pressure increases are terminated before the target deceleration rate is achieved if any limit is exceeded.
Very high pressure systems have been proposed for disk brake air systems. However, this technology cannot be operatively applied to present air brake circuits, and it is not yet approved by D.O.T.
In the past, dual pressure air brake systems have been proposed where a higher pressure (120 psi) is generated by an on-board air compressor and stored in a first tank to operate a spring air brake circuit. Air pressure at 120 psi is passed through a pressure reducing valve to be stored at a lower pressure (60 psi) to operate a service air brake circuit. This technology has no application to collision avoidance circuits.
As discussed above, existing collision avoidance systems that have been designed for hydraulic brake systems, are not applicable (transportable) to air brake systems as air brake system components and hydraulic brake system components differ remarkably. The hydraulic system technology is not transportable into air brake system technology. Moreover, existing collision avoidance systems have not been designed for aftermarket installation in older vehicles. Additionally, they have not been designed to operate with various third party warning or detection devices.
The National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety announced in March 2016, that by 2022, 99% of the new automobiles must have automatic emergency braking systems as a standard feature. Automatic emergency braking systems will similarly, also, soon be required for tractor trailers, and heavy straight trucks and buses.
The features of aftermarket installation and compatibility with existing third party warning and detection devices are important.
It is also important to be able to modify the existing air brake systems on tractor trailers, heavy straight trucks and buses, as these vehicles have long service lives, often extending beyond twenty years or more. These vehicle air brake systems should be able to be modified to meet the new NHTSA standards without replacing the entire air system.
It is desirable that the modifications to existing non-electronic air brake systems also be non-electronic, thereby eliminating or minimizing the need for sensitive electronic components.
It is further desirable that the modified system be able to operate with drive brake pedal air operation as originally installed.
It is also desirable that the system be able to operate with an automatic braking method responsive to an “impending” collision (critical) situation signal, and with an automatic braking method responsive to an “imminent” collision (more critical) situation signal (stage 3).
It is highly desirable that the modifications of the original air brake system, resident in the present invention, leaves the system pneumatically activated and controlled.